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function get_transaction (transaction_id) {
    // *Always* use this endpoint prefix for the Bango Payment API.
    const base_url = "https://api.bango.net/v5/";

    // Result value
    let transaction = null;

    try {
        // Send GET with path param to the Bango Payment API and parse the JSON response.
        let response = rest_client_call({
            method: "GET",
            url: base_url + "transaction/" + transaction_id,
            headers: {
                "Authorization": get_authorization_header(),
            },
        }).from_json();

        // The responseCode tells us the result.
        switch (response.responseCode) {
            // Success
            case "OK":
                transaction = response.transaction;
                break;

            // Merchant problems
            // These indicate issues in your code, not the Bango Platform.
            case "BAD_REQUEST":   // Invalid request
            case "UNAUTHORIZED":  // Check your credentials
            case "NOT_FOUND":  // Invalid transaction ID
                throw "Merchant implementation error";

            // Bango Platform issues
            // These likely indicate transient problems.
            // In production code, you might want to try the request again
            // after a delay, ultimately falling back to an error state.
            case "INTERNAL_ERROR":
            case "SERVICE_UNAVAILABLE":
                throw "Bango Platform unavailable"

            // This might indicate Bango has added a new response code.
            // Check the documentation again.
            default:
                throw "Unrecognized response code";
        }

    } catch (exception) {
        // Production code might want to notify the merchant in some way,
        // and/or log full details of the exception for later analysis,
        // and degrade gracefully for the user.
        output("An error occurred!");
        output(exception);
    }

    // transaction details if found, null if not found
    return transaction;
}